JP 9-84205 A, published by the Japan Patent Office in 1997, discloses a device that computes a state of charge (hereinafter abbreviated to “SOC”) for a battery by measuring a battery discharge current and adding up current values.
The battery SOC is computed by using electric current sensors capable of covering both a rated discharge range at which the battery is capable of producing continuous discharge, and a high power instantaneous rated discharge range where the battery is capable of performing discharge for a short period of time.